1. Field of the Invention
This invention relates generally to a portable telephone and, more particularly, to a portable telephone having a telephone main body, a receiver, a dial switch, a radio call circuit, and a power battery.
2. Description of the Related Art
The number of subscribers to the portable telephone system is drastically increasing due to improved performance of the component parts, better calling capabilities due to improved and more accurate radio relay stations, lower fees, as well as changes in business configuration and social environment. Therefore, demand is raised for a portable telephone that is reduced in size and weight, that is of a so-called pocket size, and which nevertheless has a transmitter, a receiver, a dial switch, a radio call circuit,a power battery and so forth.
The sheet switch configuration of the dial switch, the development of a high-performance battery, and the improved integration degree of electronic parts have led to significant reductions in weight. Nevertheless, because it is necessary for the transmitter and the receiver of the telephone to be arranged at a relative distance equal to the interval between the ear and the mouth and because of other functional constraints, the overall size of the telephone is determined by the distance between the transmitter and the receiver, that is, between the speaker the microphone.
Generally, in a telephone it is preferred to set the linear distance between the speaker and the microphone and the angle therebetween to 13.5 to 14.3 cm and about 23.3.degree. to 13.4.degree., respectively. Because of these design constraints a telephone has been proposed that is partitioned into a transmitter side section or block with the microphone and a receiver side section or block with the speaker, and these two blocks are adapted to be collapsible for reducing the overall size. One example of such a collapsible telephone is found in U.S. Pat. No. 4,845,772.
It is possible with this type of collapsible or foldable telephone to reduce its size to approximately one-half of the common telephone. Nevertheless, it is necessary to partition the control substrate, that is, the circuit board bearing the operating and control electronics, into two separate portions as well. Besides, owing to the collapsible construction, the telephone is increased in thickness and moreover is difficult to use and handle.
Meanwhile, there is disclosed in Japanese Laid Open Patent No SHO/61-198851 entitled "Speaker Microphone", a hand microphone of the type employed in a car phone having an extension microphone similar to a telephone handset, which extension microphone typically resides in a hand microphone casing and which may be pulled out of the hand microphone casing or rotated for use.
In such hand microphone in which, for example, the extension microphone is pulled out of the casing for use, it is difficult to set the relative positions of the speaker and the microphone, so that the speaker and the microphone may not be in correct correspondence with the ear and the mouth, which are disposed in a predetermined three-dimensional disposition relative to each other, such that call properties are worsened when the hand microphone is applied to the portable telephone. This problem is derived from the arrangement that the microphone is not rotatable relative to the main body.
On the other hand, if the extension microphone is adapted to be rotated relative to the casing, the relative disposition of the speaker and the microphone may be adapted so that the speaker and the microphone may be in correspondence with the ear and the mouth. Consequently, by adapting the technology to the portable telephone so that the transmitter member having built therein the transmitter is rotatably assembled to the lateral surface of the main body, it becomes possible to develop a small-sized portable telephone that is substantially the same width as and a length approximately one-half of the conventional telephone. Such a portable telephone is represented in U.S. Pat. No. 5,197,091.
Nevertheless, with the portable telephone with the rotatable extension microphone, since the extension microphone is adapted to be extended to a pre-set configuration by being rotated in a lateral direction away from a housing recess formed on one lateral surface of the telephone case, the finger ends of the hand gripping the telephone are also retaining the extension microphone, as a result of which difficulties are raised in manipulating the telephone using only one hand, as might be required with a car phone.
Moreover, because the extension microphone is of a relatively simple construction, if the hand or other object is impacted on the extension microphone, so as to apply an excessive load thereon, there is the risk of breakage of the extension microphone itself or of the rotation supporting means. Thereby raising problems in implementation of the portable telephone making use of the hand microphone technology.